Officials say Ibrahim Asiri is a lethal militant strategist who has been behind a number of attempted bombings. Meanwhile, Yemen files charges against U.S.-born radical cleric Anwar Awlaki.

Yemeni soldiers patrol the streets of Sana, the capital. Hours after a government… (Yahya Arhab / European Pressphoto…)

Reporting from Sana, Yemen — Yemeni special forces launched an offensive Tuesday in rugged terrain, searching for an Al Qaeda bomb maker believed to have designed explosives concealed in printer cartridges that were intercepted in two U.S.-bound packages last week.

The hunt for Ibrahim Asiri, a Saudi-born munitions expert, intensified in militant strongholds in Shabwa and Marib provinces. It is the third major operation against Al Qaeda in recent months but one that has taken on new urgency since a plot to blow up aircraft over the U.S. was uncovered Friday.

Investigators describe Asiri as one of Al Qaeda's most lethal strategists. He is alleged to have rigged the explosives in a 2009 suicide bombing carried out by his brother in the failed assassination attempt against Saudi Arabia's intelligence director. He also is suspected of building the bomb that was hidden in the underwear of the Nigerian student who has been charged in the bungled attempt to bring down a U.S. airliner in December.

The military incursion to find Asiri and other fighters in the group Al Qaeda in the Arabian Peninsula began the same day Yemen for the first time filed charges against American-born radical cleric Anwar Awlaki. Prosecutors accused him of "plotting to kill foreigners" in the Oct. 6 slaying of a French manager at an oil compound in Sana.

Awlaki, a charismatic speaker who has emerged as an Al Qaeda leader, will be tried in absentia with his cousin, Osman Awlaki. The charges were read during a hearing for Hisham Assem, the security guard accused of shooting the Frenchman.

Prosecutor Ali Saneaa said Assem was inspired to kill foreigners after listening to audiotapes and sermons sent to him by Awlaki. The narrative is similar to accusations by U.S. officials that Awlaki's teachings prompted a killing spree last year at Ft. Hood, Texas, allegedly carried out by an Army psychiatrist and that they were the catalyst for the Nigerian's alleged attempt to bring down the Detroit-bound plane.

"It was natural for the Yemen government to accuse Awlaki," said Saeed Ali O. Jemhi, an expert on Al Qaeda. "They had been hunting him without charges. Now they have legal justification, and it will allow the Yemen and U.S. governments to better cooperate on his capture."

The two governments, however, ultimately may be in dispute over the cleric's fate. Yemeni officials have said that Awlaki is a citizen of Yemen and will not be handed over to the U.S. The Obama administration wants to try Awlaki, who was born in New Mexico to Yemeni parents, but it also reportedly has placed him on a CIA list for assassination or capture.

Tuesday's developments indicate growing U.S. demands on the government of Yemeni President Ali Abdullah Saleh to defeat the estimated 300 to 500 Al Qaeda fighters hiding in Yemen's tribal lands, mountains and deserts. Washington has so far provided funding, equipment and training to Yemeni special forces, but the extremists have continued to strike domestically and internationally.

Hours after attacking militant redoubts, Yemeni officials blamed Al Qaeda for blowing up a section of oil pipeline operated by a South Korean firm in Shabwa province.

"The military campaign against Al Qaeda is just more propaganda," Jemhi said. "The previous campaigns achieved nothing except a few arrests. It is the result of U.S. pressure following the discovery of the package bombs."